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[英]How to conditionally ignore properties with a Jackson AnnotationIntrospector
[英]How to make Jackson ignore properties if the getters throw exceptions
我有很多類來自供應商,他們喜歡在屬性訪問上隨機拋出RuntimeExceptions。
public Object getSomeProperty() {
if (!someObscureStateCheck()) {
throw new IllegalStateExcepion();
}
return calculateTheValueOfProperty(someRandomState);
}
我無法更改類,無法添加注釋,為每個類定義mixins是不現實的,因為堆棧的這一部分經常變化。
如果傑克遜的getter拋出異常,我如何讓傑克遜忽略一個屬性?
要在Jackson中執行自定義序列化 ,您可以使用BeanSerializerModifier
注冊模塊 ,該模塊指定所需的任何修改。 在您的情況下, BeanPropertyWriter.serializeAsField
是負責序列化單個字段的方法,因此您應該創建自己的BeanPropertyWriter
,忽略字段序列化的異常,並使用BeanSerializerModifier
注冊模塊,該模塊使用changeProperties
將所有默認BeanPropertyWriter
實例替換為您自己的實現。 以下示例演示:
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.fasterxml.jackson.databind.ser.*;
import java.io.IOException;
import java.util.List;
import java.util.stream.Collectors;
public class JacksonIgnorePropertySerializationExceptions {
public static void main(String[] args) throws IOException {
ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new SimpleModule().setSerializerModifier(new BeanSerializerModifier() {
@Override
public List<BeanPropertyWriter> changeProperties(SerializationConfig config, BeanDescription beanDesc, List<BeanPropertyWriter> beanProperties) {
return beanProperties.stream().map(bpw -> new BeanPropertyWriter(bpw) {
@Override
public void serializeAsField(Object bean, JsonGenerator gen, SerializerProvider prov) throws Exception {
try {
super.serializeAsField(bean, gen, prov);
} catch (Exception e) {
System.out.println(String.format("ignoring %s for field '%s' of %s instance", e.getClass().getName(), this.getName(), bean.getClass().getName()));
}
}
}).collect(Collectors.toList());
}
}));
mapper.writeValue(System.out, new VendorClass());
}
public static class VendorClass {
public String getNormalProperty() {
return "this is a normal getter";
}
public Object getProblematicProperty() {
throw new IllegalStateException("this getter throws an exception");
}
public String getAnotherNormalProperty() {
return "this is a another normal getter";
}
}
}
上面的代碼使用Jackson 2.7.1和Java 1.8輸出以下代碼:
ignoring java.lang.reflect.InvocationTargetException for field 'problematicProperty' of JacksonIgnorePropertySerializationExceptions$VendorClass instance
{"normalProperty":"this is a normal getter","anotherNormalProperty":"this is a another normal getter"}
顯示拋出IllegalStateException
getProblematicProperty
將從序列化值中省略。
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